Duct tapes are a common and widely used type of adhesive tape. Duct tapes typically comprise a scrim, a polymer film backing, and an aggressive, rubber resin-based pressure sensitive adhesive that is coated over the scrim and the backing. The scrim provides strength to the tape and additionally allows the tape to be hand torn.
Presently, the melt blown polyethylene films used to make duct tape backings either do not contain a release material or use low molecular weight release materials (e.g., waxes) that can bloom to the free surface of the backing and provide a release function. Without the use of release material, the unwind forces of duct tapes made with such films are extremely high due to the aggressive nature of the pressure sensitive adhesive employed. However, the low molecular weight release materials are cohesively weak and are not strongly bound to the film surface; therefore, the release material can transfer to the adhesive surface when the tape roll is unwound, resulting in reduced adhesion levels.
Conventional polymeric release materials could be applied to the duct tape backing in a separate step, but this adds additional cost to the resulting product. Alternatively, a polymeric release material could be mixed with an extrudable polymer, for example, polyolefin and extruded to form a release layer. However, incompatibility between these materials often requires that the polymer and the polymeric release material be pre-blended and pelletized to provide a homogeneous feed for an extruder. This blending and pelletizing process adds additional cost to the resulting tape backing.
In view of the foregoing, what is desired is an adhesive tape backing that includes a release layer comprising a polymeric release material that can be produced via a coextrusion process wherein the materials making up the release layer can be fed directly to an extruder without first mixing and pelletizing. Desirably, the resulting release layer will not transfer to a pressure sensitive adhesive.